Affinity Photo
Adding A Gradient With A Mask
Rather than trying to add a gradient to a mask, which you may have trouble editing later if its needed. It is better to add a mask to the gradient on a Fill Layer. Allowing you to alter the gradient as many times as you feel like it is needed.
Pixabay Image Used
https://pixabay.com/photos/luxury-home-upscale-architecture-2409577/
Written version you can download
Short But Sweet – Issue 6
A Written Tutorial For Affinity Photo
Adding Gradient With A Mask
https://www.dropbox.com/s/l96px7ekkkx2fj9/Affinity%20Photo%20-%20Short%20But%20Sweet%20issue%206%20-%20Adding%20A%20Gradient%20With%20A%20Mask.pdf?dl=0